The Rational
When it comes to the power jQuery Mobile (jqm) to help us organize our code we could pretty much say it in one hyphened word: "non-existent".How could this pass with such a popular library. Well, the simple answer is that it is by design. This does not mean, however, that you should not organize your jqm code projects. You are free to use any JavaScript organizing principle or helper library, e.g. BackBone or Ember, you like. Jqm's focus is the page paradigm and rendering of touch friendly UI.
This, of course, does mean that you have your work cut out for you to make decisions surrounding your project. Looking at very common pattern of jqm apps, they tend to be an amalgamation of different libraries that have many layers of code and logic that needs to be organized. And, needless to say, there is always seems to be a little bit of overlap in library's coverage, e.g. if you used Backbone for route handling, we will need to turn off the native jqm methodology etc.
In the particular approach I am outlining in this post, the goal was to use minimal amount of libraries while still creating convention based organization of code, ui, and data. We should be able to split our program into distinct parts that the browser can load when needed.
This will help us in following manner:
- decoupling of presentation and logic
- modular JavaScript code
- decoupling of the page paradigm from singular page apps
- organization of code by convention
Overall, the maintenance of our program should be easier, while adding new parts becomes child-play ;o)
After a little experimentation, I decided the only thing needed was a little extra JavaScript and the RequireJS library. Let me explain how.
The Setup
Standard application initialization occurs through the index.html page. However, unlike most JS apps there is only one <script> tag and that tag loads RequireJS. Thereafter the application parts are either loaded by RequireJS or JQM page loader. Thus, the script tag jungle is avoided. Clean abstractions of dependencies and libraries are all captured in the RequireJS config file.Since this is a sample app it makes liberal use of console.log function.
<script data-main="app/config" src="libs/require.js"></script>
Also something that is different here is the externalized page header. I did not add an externalized page footer which can be easily done but was not needed for my example. An externalized header can easily be repeated on each subsequently loaded jqm page and thus we can focus on the page content. We will still change the header display dynamically and add proper navigation as we move between pages.
<!-- external header used on all pages we will hide buttons dynamically -->
<header data-theme="b" data-role="header" data-title="Simple App" data-position="fixed">
<a id="btnHome" data-rel="back" data-transition="slide"
class="ui-btn ui-shadow ui-corner-all ui-icon-arrow-l ui-btn-icon-notext ui-btn-inline"
title="move back">back</a>
<h1></h1>
<a href="#info" id="btnInfo"
class="ui-btn-right ui-btn ui-btn-inline ui-btn-icon-notext ui-mini ui-corner-all ui-icon-info"
title="">Info</a>
</header>
The Application Structure
The application is structured in such a fashion that a certain convention can be observed.The main directories under /app are
- controllers
- data
- pages
- services
- stores
All code files except the RequireJS config file are in a slightly modified JavaScript AMD Module format.We are also caching jqm views (pages) once they have been loaded using the jqm domCache directive:
$.mobile.page.prototype.options.domCache = true;
controllers
This is where we place all controller logic for our views. I maintained a convention where views do not have any logic or binding and minimal links. Controllers are automatically loaded and initialized based on the view (page) that is being requested. The app will check for a similarly named controller and start the process. Thus, all page behavior, event binding, business logic would be handled here.If the controller exports (or exposes) a function named "init", that function will be called after each page load or display.
The overall convention for the controller loading process and application behavior are coded into start.js module. It acts as the overall controller for the application.
Here is the basic controller construct example.
//controller sample
define(
function() {
console.log("empty controller loaded");
//public (export)
return {
init: function(){
console.log("init was called")
}
}
});
data
I have placed a file containing a json array of objects into this file. Thus, we can refer to this as our "database". This is not a convention that is enforced on the code layer. I chose to abstract data in this fashion. It could easily be extended to be the connection layer to a database API etc.pages
The pages in our app are the view of the MVC model. I chose to use very simple views. These are snippets of HTML just with the JQM markup needed to render a basic skeleton. Logic that changes the view is either in controller or services layer.Here is an example of a view. It is just the date-role="page" part of the jqm html markup.
<section data-role="page" id="composerDetail" data-title="Composer Detail">
<div role="main" class="ui-content">
<h2 id="composerName">Composer Name</h2>
<hr>
<!-- composer info -->
<div class="ui-grid-a ui-responsive" >
<div class="ui-block-a center" style="width:20%;">
<div class="">
<img id="composerImage" src="" alt="composer image" style="vertical-align: middle;">
</div>
</div>
<div class="ui-block-b" style="width:80%; vertical-align: top;">
<div class="ui-body ui-body-d"><p id="composerDescription">composer information</p></div>
</div>
</div>
<!-- buttons -->
<div class="ui-grid-a center" >
<div class="ui-block-a" style="width:20%;">
<div class="ui-body ui-body-d"><a data-rel="back" data-transition="slide" class="ui-btn ui-shadow ui-corner-all ui-icon-arrow-l ui-btn-icon-notext ui-btn-inline" title="Back to composer list">back to list of composers</a></div>
</div>
<div class="ui-block-b" style="width:80%;">
<div class="ui-body ui-body-d">
<button id="btnWiki" class="ui-btn ui-icon-arrow-u-r ui-btn-icon-right ui-corner-all" title="More information on WikiPedia" style="width:80%">WikiPedia</button>
</div>
</div>
</div>
</div>
</section>
services
This is where I paced example services that can be used in other modules. In my case just a way to abstract jquery ajax calls and handle generic responses. But, this could be easily expanded to anything that is shareable across the modules or detailed implementation that would be make controllers large and unwieldy. This is not a enforced by code but a convention I am suggesting. It helps to separate heavy logic into distinct modules for maintainability.stores
I used the stores to abstract interaction with the data layer. For example my sample ComposersDataStore.js in this project can sort the composers, return a specific one etc. This is also not enforced by code, but rather a convention I am proposing for your app build.The Init Process
After loading of the index.html a list of dominoes begins to fall- Require will load config.js which contains the environment definition and load dependencies.
- config.js will, in turn, load the start.js module which contains our overall application controller
- config.js will also switch to the "main" page (view) which will trigger common actions by the overall application controller as defned in start.js:
- Load the main view (main.htm)
- Load the main_controll.js controller
- Call the init function of main controller
Thereafter it is up to the user and his/her interactions which pages will be loaded and which actions will be triggered.
Unfortunately there seems to be a bug in the jQuery Mobile page loading (page widget) which makes initialization phase inconsistent. The process is not always kicked of correctly so it required for me to do a check in the index.html itself. If we did not find the main controller module loaded after 5 seconds, we would switch to the main view one more time, which triggers the part 3 and seems to fix things. This loaded the app consistently across all devices.
setTimeout(function(){
if (!require.defined("controllers/main_controll")) {
console.log("catch all triggered.");
$( ":mobile-pagecontainer" ).pagecontainer( "change", "app/pages/main.htm", { showLoadMsg: true } );
}
},5000)
The Hook
The element that drives the main convention of this app is implemented in the pagecontainerchange event hook. This event is exposed by jQuery mobile.
$(document ).on( "pagecontainerchange", function() {}
Here we automatically load the appropriate controller based on the id of the view (page) and initialize and call the init() function of the module. In addition, we change display name of the view based on what is in the data-title of the jqm view definition. All this happens in the start.js application controller.
Of course, in a more opinionated implementation, additional conventions could be coded here; for example, automatic loading of data-stores and even binding of the store's fields to form elements. Thus, the concept can be expanded. Experiment and see if you could add to it.
GitHub baby
The complete project can be reviewed or downloaded from GitHub. I have included the libraries and versions of jQuery and RequireJS so things should be able to work out of the box:Expanded Project for Download from GitHub
Enjoy,
B.
